It is the purpose of this investigation to document the effects of changing pH and Al, Cu, Pb and Zn toxicity on freshwater lake algae. We will focus the study on cellular changes and the growth rates of the algae at different pH in the presence and absence of Al, Cu, Pb and Zn. Specifically, the objectives of this study are: 1. Determine the effect of changing pH from 11.0 to 4.0 on the growth of selected representative freshwater like algae. 2. Determine the EC50 of Al, Cu, Pb and Zn at the different pHs used in this study. 3. Determine cellular effects using morphometry at the different pHs tested and the effect of Al, Cu, Pb and Zn at the EC50 and one log concentration above and below this point. 4. Determine the effect of each treatment on the chlorophyll content of the cells. This is a good estimate of productivity. 5. Determine using X-ray energy dispersive analysis with a scanning transmission electron microscope if compartmentalization of the Al, Cu, Pb and Zn has occurred. 6. To establish the toxicity hierarchy among these four cations at the varying pH levels in order to determine the importance of Al as a key toxicant in acidogenesis. We feel there is an urgent need to elucidate the impact of acid rain on our freshwater lakes which is slowly turning them into acid lakes. One set of data which seems to be lacking but is critical to our assessment of this problem is solid scientific data which unequivocally demonstrates the suggested effect of acid rain, via pH alterations in mobilized metal effects on algal systems.